| 1. |
- Bruehwiler, Paul A., et al.
(författare)
-
Comparison of quasistatic to impact mechanical properties of multiwall carbon nanotube/polycarbonate composites
- 2010
-
Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 25:6, s. 1118-1130
-
Tidskriftsartikel (refereegranskat)abstract
- We report the quasistatic tensile and impact penetration properties (falling dart test) of injection-molded polycarbonate samples, as a function of multiwall carbon nanotube (MWNT) concentration (0.0-2.5%). The MWNT were incorporated by dilution of a commercial MWNT/polycarbonate masterbatch. The stiffness and quasistatic yield strength of the composites increased approximately linearly with MWNT concentration in all measurements. The energy absorbed in fracture was, however, a negative function of the MWNT concentration, and exhibited different dependencies in quasistatic and impact tests. Small-angle x-ray scattering (SAXS) showed that the dispersion of the MWNT was similar at all concentrations. The negative effects on energy absorption are attributed to agglomerates remaining in the samples, which were observed in optical microscopy and SAXS. Overall, there was a good correspondence between static and dynamic energy absorption.
|
|
| 2. |
- Georgiadis, Marios, et al.
(författare)
-
Nanostructure-specific X-ray tomography reveals myelin levels, integrity and axon orientations in mouse and human nervous tissue
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method’s sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures.
|
|
| 3. |
- Liebi, Marianne, 1984, et al.
(författare)
-
Small-angle X-ray scattering tensor tomography: Model of the three-dimensional reciprocal-space map, reconstruction algorithm and angular sampling requirements
- 2018
-
Ingår i: Acta Crystallographica Section A: Foundations and Advances. - 2053-2733. ; 74:1, s. 12-24
-
Tidskriftsartikel (refereegranskat)abstract
- Small-angle X-ray scattering tensor tomography, which allows reconstruction of the local three-dimensional reciprocal-space map within a three-dimensional sample as introduced by Liebi et al. [Nature (2015), 527, 349-352], is described in more detail with regard to the mathematical framework and the optimization algorithm. For the case of trabecular bone samples from vertebrae it is shown that the model of the three-dimensional reciprocal-space map using spherical harmonics can adequately describe the measured data. The method enables the determination of nanostructure orientation and degree of orientation as demonstrated previously in a single momentum transfer q range. This article presents a reconstruction of the complete reciprocal-space map for the case of bone over extended ranges of q. In addition, it is shown that uniform angular sampling and advanced regularization strategies help to reduce the amount of data required.The mathematical framework and reconstruction algorithm for small-angle scattering tensor tomography are introduced in detail, as well as strategies which help to reduce the amount of data and therewith the measurement time required. Experimental validation is provided for the application to trabecular bone.
|
|
| 4. |
- Martiel, Isabelle, et al.
(författare)
-
Low-dose in situ prelocation of protein microcrystals by 2D X-ray phase-contrast imaging for serial crystallography
- 2020
-
Ingår i: IUCrJ. - 2052-2525. ; 7, s. 1131-1141
-
Tidskriftsartikel (refereegranskat)abstract
- Serial protein crystallography has emerged as a powerful method of data collection on small crystals from challenging targets, such as membrane proteins. Multiple microcrystals need to be located on large and often flat mounts while exposing them to an X-ray dose that is as low as possible. A crystal-prelocation method is demonstrated here using low-dose 2D full-field propagation-based X-ray phase-contrast imaging at the X-ray imaging beamline TOMCAT at the Swiss Light Source (SLS). This imaging step provides microcrystal coordinates for automated serial data collection at a microfocus macromolecular crystallography beamline on samples with an essentially flat geometry. This prelocation method was applied to microcrystals of a soluble protein and a membrane protein, grown in a commonly used double-sandwich in situ crystallization plate. The inner sandwiches of thin plastic film enclosing the microcrystals in lipid cubic phase were flash cooled and imaged at TOMCAT. Based on the obtained crystal coordinates, both still and rotation wedge serial data were collected automatically at the SLS PXI beamline, yielding in both cases a high indexing rate. This workflow can be easily implemented at many synchrotron facilities using existing equipment, or potentially integrated as an online technique in the next-generation macromolecular crystallography beamline, and thus benefit a number of dose-sensitive challenging protein targets.
|
|
| 5. |
- Nygård, Kim, 1978, et al.
(författare)
-
Size-dependent shape evolution of patterned polymer films studied in situ by phase-retrieval-based small-angle x-ray scattering
- 2012
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 45:14, s. 5798-5805
-
Tidskriftsartikel (refereegranskat)abstract
- Patterned polymer films are known to exhibit shape evolution when annealed at temperatures close to or above the glass transition temperature. Here, we employ small-angle X-ray scattering to address the size-dependent shape evolution of poly(methyl methacrylate) (PMMA) gratings obtained by thermal nanoimprint lithography. Using an iterative phase-retrieval scheme, we reconstruct the height profile of the grating in situ in a model-independent manner during a heating ramp through the glass transition. This allows us to directly observe the evolution from a trapezoidal shape, via a sinusoidal-like one, into a flat film, in agreement with ex-situ atomic force microscopy experiments. Moreover, we find the onset temperature of shape evolution to decrease monotonically with decreasing pattern size, the difference being 4 °C between gratings with periods of 240 and 80 nm. We primarily attribute the size-dependent shape evolution to a reduction in viscosity with decreasing pattern size, which is induced by either free-surface effects or surface-tension-driven non-Newtonian flow.
|
|
